ByJulie Pace, Associated PressMay 14, 2015

Camp David, Md. — President Barack Obama pledged America's "ironclad commitment" to anxious Persian Gulf nations Thursday to help protect their security, pointedly mentioning the potential use of military force and offering assurances that a potential nuclear agreement with Iran would not leave them more vulnerable.

At the close of a rare summit at the presidential retreat at Camp David, the president said the US would join the Gulf Cooperation Council nations "to deter and confront an external threat to any GCC state's territorial integrity." The US pledged to bolster its security cooperation with the Gulf on counterterrorism, maritime security, cybersecurity, and ballistic missile defense.

"Let me underscore, the United States keeps our commitments," Mr. Obama said at a news conference.

Thursday's meeting at Obama's retreat in the Maryland mountains was aimed at quelling the Gulf's fears of US-led nuclear talks with Iran. Gulf states worry that if Iran wins international sanctions relief, the influx of cash would embolden what they see as Tehran's aggression in the region.

The president acknowledged those concerns, but said the US believes Iran's focus would be on shoring up an economy that has struggled under the sanctions pressure.

Obama and top advisers walked the Gulf nations through the work-in-progress nuclear deal in detail during private meetings Thursday. The president said that while the Gulf leaders hadn't been asked to "sign on the bottom line" to approve the framework, they did agree "that a comprehensive, verifiable solution that fully addresses the regional and international concerns about Iran's nuclear program is in the security interests of the international community, including our GCC partners."

Saudi Foreign Minister Adel al-Jubeir said Arab leaders were "assured that the objective is to deny Iran the ability to obtain a nuclear weapon" and that all pathways to such a weapon would be cut off.

He added that it was too early to know if a final nuclear agreement would be acceptable, saying, "We don't know if the Iranians will accept the terms they need to accept."

The US and five other nations are working to finalize the nuclear deal ahead of an end of June deadline.

As if to underscore Gulf concerns, an Iranian naval patrol boat fired on a Singapore-flagged commercial ship in the Persian Gulf Thursday. A US official said it was an apparent attempt to disable the ship over a financial dispute involving damage to an Iranian oil platform.

The incident took place a bit south of the island of Abu Musa just inside the Gulf, according to the US official, who was not authorized to discuss details by name. The White House said no Americans were involved in the incident.

Ben Rhodes, Obama's deputy national security adviser, said that while the incident did not come up in Thursday's discussions, it was "exactly the type of challenge" the Gulf nations are focused on.

Mr. al-Jubeir, for his part, said, "the Iranians should not be allowed to get away with it."

Obama has said he shares the Gulf's concerns about Iran's activities in the region. The US has criticized Iran's support for Hezbollah, as well as attacks carried out by Iran's Quds Force. In 2011, the Obama administration accused Iran of plotting to kill the Saudi ambassador to the United States in Washington.

Thursday's summit marked an unusual investment by Obama in his relationship with the Gulf. He rarely uses Camp David for personal or official business, but White House aides hoped the more intimate setting would lead to a more candid conversation with the Arab allies.

Just two other heads of state – the emirs of Qatar and Kuwait – joined Obama at Camp David. Saudi Arabia, United Arab Emirates, Oman, and Bahrain all sent lower-level but still influential representatives.

As the leaders gathered around a large table in the Laurel lodge, the most notable absence was Saudi King Salman. On Sunday, Saudi Arabia announced that the king was skipping the summit, two days after the White House said he was coming.

The White House and Saudi officials insisted the king was not snubbing Obama. But there are indisputable signs of strain in the long relationship between the US and Saudi Arabia, driven not only by Obama's Iran overtures but also by the rise of Islamic State militants and a lessening US dependency on Saudi oil.

Among the other issues discussed at the summit were the US-led campaign against the Islamic State, the fighting in Syria, and the intractable conflict between Israelis and Palestinians.

The Saudis are also particularly concerned about the situation in Yemen, where Houthi rebels with ties with Iran have ousted the US- and Saudi-backed leader.

For more than a month, a Saudi-led coalition has tried to push back the Houthis with a bombing campaign. A five-day humanitarian cease-fire went into effect Tuesday, though the pause in fighting was at risk amid a series of violent incidents.